Update defaults to support arbitrary start frames

Currently, Blender assumes that the start frame of an animation is going to be frame 1. However, studios generally start at frame 101 or 1001 due to two reasons:

1. This helps force the frames to be padded. For example, if the start frame is 1001, then we have up to frame 9999 before we either need to add zero padding or file sorting fails.
2. This allows for pre-roll for simulations. For example, if we have 50 frames of pre-roll for a cloth simulation to help let it settle, then starting a shot at 1001 means that the pre-roll starts at frame 951, where starting at frame 1 means that the pre-roll starts at frame -49 (which may not be well supported in certain situations).

Blender's current scene frame range and render systems supports this well. Set the frame range to 1001 to whatever, and it works. However, loading an image is tricky, because the image node will automatically default the animation to start on frame 1 of the scene, even though we might want it to start at frame 1001.

Here's a test case:

1. Create a new texture sequence called something like texture.1001.exr , texture.1002.exr , and texture.1003.exr
2. Create a new Blender scene with the frame range 1001 - 1003.
3. Either using the default cube/material, or a new object and/or material, create a new image texture node, and load the texture sequence. Make sure that the load texture dialog will not try loading UDIM textures, but instead only try loading image sequences.
4. The image texture's node should read "Frames 3", "Start Frame 1", "Offset 1000". This causes the rendered start frame for the first frame to be 1.

I'd like a way to easily say "This image should use an 'absolute' frame range" where it skips the start frame and frame duration information and instead picks an image based on the logic {current_frame} + {offset} , and the offset will always default to 0. Possibly via a toggle in the image texture node between the current (relative?)/absolute, and the file browser (use absolute frame range).